Such a circuit-breaker is described in French Pat. No. 79 05478 filed Mar. 2, 1979 and in French Pat. No. 80 16222 filed July 23, 1980. Reference may also be made to U.S. Pat. No. 4,421,962 which claims priority from the latter French patent.
The circuit-breakers described in these patents have the following feature: the device for inserting the closure resistance is located in the circuit-breaking chamber while the closure resistance itself is disposed in a housing which is coaxial with the circuit-breaking chamber and which extends axially therefrom. The inside of the housing is in communication with the circuit-breaking chamber and is therefore filled with dielectric gas at the same pressure as in the chamber.
This disposition has numerous advantages which are described in said prior patents, and in particular it reduces the bulk and the cost of the circuit-breakers.
Nevertheless there is a drawback: a circuit-breaker made as described in the patents is very long because of the housing containing the closure resistance. As a result such a circuit-breaker is difficult to transport from the factory to the site where it is to be installed, since it must be transported as a single unit. There is no question of separating the circuit-breaking chamber and the housing for transport purposes since it would then be necessary to fill them with dielectric gas on site where safety conditions for proper filling are difficult to obtain.
Further, users desire to be able to replace one or more components of the resistance on site without putting the inside of the circuit-breaking chamber into communication with the atmosphere since that would require subsequent refilling with dielectric gas, which is difficult to do, on site.
An aim of the invention is to provide a circuit-breaker having a closure resistance placed in a housing which extends the circuit-breaking chamber and which is in communication therewith, but which is made in such a manner as to enable the housing to be separated from the chamber and reassembled therewith without loss of gas either from the chamber or from the housing.
This would make it possible to fill the circuit-breaker with dielectric gas in a factory having all the necessary facilities. It could then be transported to its installation site as two separate units, thereby facilitating transport and handling. Finally it could be assembled on site without there being any need to perform dielectric gas filling operations.
If the closure resistance needs to be totally or partially replaced, only the housing would need putting into communication with the atmosphere, with the chamber remaining filled with dielectric gas.